package wwj;

import java.text.DecimalFormat;
import java.util.List;
import java.io.IOException;
import java.util.StringTokenizer;

import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.Path;
import org.apache.hadoop.io.DoubleWritable;
import org.apache.hadoop.io.IntWritable;
import org.apache.hadoop.io.LongWritable;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.mapreduce.Job;
import org.apache.hadoop.mapreduce.Mapper;
import org.apache.hadoop.mapreduce.Reducer;
import org.apache.hadoop.mapreduce.lib.input.FileInputFormat;
import org.apache.hadoop.mapreduce.lib.output.FileOutputFormat;

import wwj.reader.CsvReader;

/*
 * hadoop jar /home/hadoop/桌面/boot.jar UserRankAvg /work/ratings.csv  /work/output/UserRankAvg/2

 */
public class UserRankAvg {

	public static class MMapper extends
			Mapper<Object, Text, Text, IntWritable> {

		public void map(Object key, Text value, Context context)
				throws IOException, InterruptedException {
			List<String> list = CsvReader
					.readLine(value.toString());
			if (list.get(0).indexOf("User") != -1)
				return;
			String uid = list.get(0);
			int rating = Integer.parseInt(list.get(2));
			context.write(new Text(uid), new IntWritable(rating));

		}
	}

	public static class MReducer extends
			Reducer<Text, IntWritable, Text, DoubleWritable> {

		public void reduce(Text key, Iterable<IntWritable> values,
				Context context) throws IOException,
				InterruptedException {
			long sum = 0;
			long cnt = 0;
			for (IntWritable val : values) {
				sum += val.get();
				cnt++;
			}
			DecimalFormat df = new DecimalFormat("#.0000");
			double avg = Double.parseDouble(df.format(sum * 1.0
					/ cnt));

			context.write(key, new DoubleWritable(avg));

		}
	}

	public static void main(String[] args) throws Exception {
		Configuration conf = new Configuration();
		String[] otherArgs = args;
		if (otherArgs.length < 2) {
			System.err.println("Usage:  <in> [<in>...] <out>");
			System.exit(2);
		}
		Job job = new Job(conf, "UserRankAvg");
		job.setJarByClass(UserRankAvg.class);
		 
		job.setMapperClass(MMapper.class);

		job.setReducerClass(MReducer.class);
		job.setMapOutputKeyClass(Text.class);
		job.setMapOutputValueClass(IntWritable.class);
		job.setOutputKeyClass(Text.class);
		job.setOutputValueClass(DoubleWritable.class);
		for (int i = 0; i < otherArgs.length - 1; ++i) {
			FileInputFormat.addInputPath(job,
					new Path(otherArgs[i]));
		}
		FileOutputFormat.setOutputPath(job, new Path(
				otherArgs[otherArgs.length - 1]));
		System.exit(job.waitForCompletion(true) ? 0 : 1);
	}
}
